Questions regarding new platform port (was Re: Porting NetBSD to the Zipit Z2 XScale handheld)

["." <lausgans%gmail.com@localhost>]

> I'm interested in porting NetBSD to the Zipit Z2 clamshell device (poor-man's analog of Sharp Zaurus).

I'm back to this. Ok, uimgs are now working when built from HEAD. At
least I see NetBSD stage-2 loader mention on the screen.
However I've switched to QEMU (which has Z2 support), since I can't
solder serial port on an actual device. And here came some questions:

1) It's easy to add new device support to Linux, as all low-level
machine initialization is already there and is common (at least for
arm/mach-pxa). Here's the whole Z2 support for example:
https://github.com/torvalds/linux/commit/b637799248520d711f0fdc64666131c1c869cfbc
However this is untrue for NetBSD. Even though the SoC code is here,
every new platform port requires reimplementation of start.S and
machdep.c. Why? What should be my sources to write them with small
losses?

2) The only PXA270 kernel (amongst zaurus, hpcarm's WZERO3 and
evbarm's GUMSTIX I know) which successfully inits the console on Z2
emulator is GUMSTIX (only U-Boot binary works though).
It panics with "pmap_map_chunk: no L2 table for VA 0xc0700000" then.
Here's the log with VERBOSE_INIT_ARM: http://pastebin.com/gtBqKFj8
Gumstix's memstart=0xa0000000 is correct here (Z2 RAM is 0xa0000000-0x2000000).
memsize=0 means size detection asm routines are not appropriate ones
for Z2. I've set memsize to KERNEL_VM_BASE - KERNEL_BASE (16M) after
that, but it doesn't help.
How to fix this?